Development of a homogeneous liquid-liquid microextraction method using lighter than water solvents for the extraction of some pesticides from distillate samples followed by GC-FID determination.

In this work, an efficient sample preparation method for the extraction and preconcentration of some pesticides from different distillate samples based on a homogeneous liquid-liquid microextraction method was developed. For this aim, in a glass test tube specially designed with a capillary tip, a standard solution of the analytes along with a few µL of n-hexanol was added and vortexed to obtain a homogeneous solution. Then, µL-volume of di-n-butyl ether was added. After vortexing, a turbid solution was obtained. After centrifuging, the organic phase, including the extracted analytes, was collected at the beginning of the capillary part of the tube. Then, an aliquot of the organic phase was injected into a gas chromatograph equipped with a flame ionization detector. Different parameters, including solvent type, solvent volume, centrifuging time, vortexing time, and pH, were optimized. In this work, high enrichment factors (160-662) and well-linear calibration curves (r 2 = 0.986-0.999) were obtained. The limits of detection and quantification were obtained in the ranges of 0.11-0.55 and 0.35-1.83 µg L-1, respectively. The precision of the procedure was examined via relative standard deviation for both intra-day (n = 7) and inter-day (n = 3) repeatabilities. Intra- and inter-day repeatabilities at a concentration of 25 µg L-1 (for each pesticide) were obtained in the ranges of 3.6-13.2% and 5.8-13.3%, respectively. Intra- and inter-day repeatabilities at the concentration of 100 µg L-1 were obtained as 3.9-7.7% and 5.1-9.9%, respectively. The useful points of this method were a short extraction time, simple implementation, low cost, and environmental compatibility.